A BBC screenshot shows the shooting incidents.

Witness describes how police officer was stabbed

At least seven people are reported to have been injured near the British Parliament, according to witnesses and media reports.

The Metropolitan Police said it is calling the event a terrorist incident until they find out otherwise.

One woman has died and other people are being treated for "catastrophic" injuries after, British news agency Press Association reported citing a junior doctor at a central London hospital.

A man driving a sports utility vehicle is believed to have run over pedestrians on Westminster Bridge around 2.40 pm local time. The driver then crashed into railings, got out of the car and attacked a policeman with a knife near the Palace Yard entrance to the House of Commons, before being shot.

David Lidington, the Leader of the House Commons, told members of parliament that police had shot an alleged assailant.

He told MPs: "Colleagues will have appreciated that events have been moving rapidly and I want to emphasize that the knowledge that I have which is definite is, so far, very limited. What I am able to say to the House is that there has been a serious incident within the estate. It seems that a police officer has been stabbed; that the alleged assailant was shot by armed police. An air ambulance is attending the scene to remove the casualties. There are also reports of further violent incidents in the vicinity."

The sitting of the House of Commons was suspended and MPs were told to stay in the chamber. All other government buildings were placed under "lock down". Theresa May, the Prime Minister, was said to be safe.

Witnesses described how a car plowed into pedestrians on Westminster Bridge before crashing into railings.

Rados?aw Sikorski, a Polish politician, told the BBC he saw four people on the ground on the bridge.

"I didn’t see a car, but I heard what I thought was a collision," he said. "I looked through the window of the taxi and I saw someone down obviously in great distress."

London police tweeted: "We were called at approx 2:40 pm to reports of an incident at #Westminster Bridge. Being treated as a firearms incident - police on scene".

Quentin Letts, a journalist tweeted: "Just saw Parliamentary security men shoot a man who had attacked a policeman. Impressive reaction times by police."

An injured person is assisted after an incident on Westminster Bridge in London, Britain March 22, 2017.??[Photo/Agencies]